I don't find I ever make off-by-one errors with simple collection iteration; at some point "i < len" becomes tattooed on your brain stem. The off-by-one errors

I don't find I ever make off-by-one errors with simple collection iteration; at some point "i < len" becomes tattooed on your brain stem. The off-by-one errors I tend to make are related to implementation details of certain data structures or algs. Really, I would describe them more as "thinking at the margins can be challenging." Correctly handling doubly linked lists, that sort of thing. Oh, and slicing. I will never get Python slicing right the first time. The fact that the range is [begin, end) is just never the way I expect it to work.